Fluid delivery system

ABSTRACT

A high pressure fluid delivery system is disclosed in which two or more guns, each having a high pressure nozzle outlet and a low pressure dump outlet, may be connected to and operated from the same pump. Pressure responsive control apparatus is provided in the flow line between each gun and the pump and each such apparatus includes a valve responsive to the fluid pressure at its respective gun for directing fluid either directly to such gun when flow is through the gun nozzle, or through an orifice in said apparatus substantially the same size as the nozzle orifice of such gun when the gun is dumping.

United States Patent [191 Pacht et a1.

[11] 3,834,621 [451 Sept. 10, 1974 Filed:

Appl. N0.: 297,216

FLUID DELIVERY SYSTEM lnventors: Amos Pacht; Hubert E. Magee, Jr.,

both of Houston, Tex.

Assignee: Partek Corporation of Houston,

Houston, Tex.

Oct. 13, 1972 US. Cl 239/76, 137/110, 239/444 Int. Cl. F 16k 21/00 Field of Search 239/76, 304, 312, 442,

References Cited UNITED STATES PATENTS Thompson 239/76 Arant 239/446 X Hipp 137/110 X Hinrichs 239/447 X Primary Examiner-Lloyd L. King Assistant Examiner-Andres Kashnikow Attorney, Agent, or Firm-Hubbard, Thurman, Turner & Tucker [57] ABSTRACT zle, or through an orifice in said apparatus substantially the same size as the nozzle orifice of such gun when the gun is dumping.

11 Claims, 10 Drawing Figures 3 39 i WATER 3 L IN i 26 2 2 35bg 27 I it:

258* EMF" 1 550 \z 24 T 31 t 28 I311 i KY. I 4

, v I '2 8 \2O 37 PATENTEDSEH 0mm SHEET 1 0F 2 bhm Fm i qmm FLUID DELIVERY SYSTEM This invention relates to a high pressure fluid delivery system and in one of its aspects to pressure control apparatus for providing substantially constant pressures from a pump delivering fluid to the system.

In the prior art, fluid systems are provided in which a high pressure stream of water, i.e., at pressures of 6,000 10,000 pounds or more, are used for many cleaning applications. In these systems one or more hand-held valve'assemblies or guns are provided, and are connected by a hose to a common outlet of a pump. The guns generally include a housing having a valve therein, a barrel extension for directing the high p'ressure stream of water through a nozzle to the object to be cleaned, a handle or trigger mechanism for operating the valve, and a relatively unrestricted pressure relief or dump outlet for relieving pressure in the assembly when flow through the high pressure nozzle outlet is interrupted by operation of the valve. When the gun is dumping water, pressures are generally no more than a few hundred pounds, and a sudden reduction on the load or the pump occurs.

Because of the wide differential between water pressures when water is dumped and when it is being discharged through the gun nozzle, apparatus have been suggested for automatically decreasing the pump engine speed during dumping, such as shown in US. Pat. No. 3,335,962. However, where two or more nozzle guns are employed in random operation, such apparatus is generally not practical. When two or more guns are used from a single source, it is highly desirable that a constant inlet pressure to the guns be provided independent of the operation of the guns. In US. Pat. No. 3,375,980, a system is provided wherein when a nozzle gun is not discharging high pressure fluid, the fluid is passed through an orifice that was substantially the same size as the guns nozzle orifice. Thus, whether a gun is discharging through its nozzle or not, a substantially constant pressure is provided by the pump. However, this system requires the use of a separate source of compressed air, a diaphragm valve assembly for each gun for switching between the gun and the added orifice, pneumatic control means on each gun for operating the diaphragm valve, and a considerable amount of additional piping. The addition of the additional pneumatic system thus represents a substantial added expense, a source of frequent maintenance and leakage problems, and generally unduly complicates the fluid delivering system. Also, the guns employed are of special design and are not dump guns which are readily available and generally preferred since the operator is always assured that the high pressure is being relieved.

It is thus an object of the present invention to provide a high pressure fluid delivery system in which two or more dump guns of standard design may be supplied fluid by a single pump, and in which a substantially constant pressure is provided by the pump during dumping operation of any of the guns.

Another object of this invention is to provide such a system which does not require an added pneumatic control system or specially designed guns.

Another object of this invention is to provide such a system in which control apparatus for a plurality of guns may be provided in one unitary assembly installed in the flow line between the pump and the nozzle guns to accomplish above mentioned objects, and in which no additional piping need be installed.

Another object of this invention is to provide such a system in which a plurality of guns with different size nozzle openings can be used at the same time, and the nozzle sizes of each gun can be easily changed.

Another object of this invention is to provide such a system in which different flow rates from the pump, or from different pumps used with the system, can be compensated for without substantially altering the systern.

Another object of this invention is to provide such a system in which the above objects can be accomplished without the need for the addition of relatively expensive, complicated, or large components.

These and other objects of this invention, which will be apparent upon consideration of the appended drawings and claims, and the following detailed description, are accomplished in the preferred embodiment illustrated by providing a fluid pressure control apparatus between each gun of a fluid discharge system and the pump of the system for maintaining a substantially constant load on the pump. Each such control apparatus includes a main flow passageway having a valve therein, and a by-pass flow passageway having an orifice sized to provide substantially the same pressure drop across the control apparatus, which is generally provided by providing substantially the same size orifree as the discharge orifice of the gun connected to the control apparatus. The valve is responsive to the pressure of fluid flowing to the gun connected to the control apparatus and when the gun is discharging fluid at high pressure through its nozzle, flow in the control apparatus is through its main passageway. However, when the gun is dumping, the valve in the respective control apparatus responds to the change in pressure at the outlet of said control apparatus to close the main passageway and direct fluid through the orifice in the bypass passageway. One or more of the described control apparatus for controlling one or more nozzle guns can be provided in a unitary assembly connected at a common inlet to a pump, and at a plurality of outlets to the respective guns, so that the assembly also functions as a manifold for directing fluid to the various guns, and no additional piping is needed. Also, since each of the control apparatus described is actuated by back pressure from the guns, a separate pneumatic or other fluid systems for control is not required.

Also, the orifice in the by-pass passageway can be provided by a threaded insert member which can be easily removed and replaced by another such member with a different size orifice when the nozzle of the gun is changed.

A pressure responsive piston is preferrably provided for moving the valve member to open and close the main passageway, and the piston is normally biased by a spring to cause the valve member to close the main passageway. in order to compensate for different pumps with different flow rates, a removable cap is provided on the housing of the control apparatus to permit the size of the spring biasing the valve member closed to be easily changed. Also, a tell-tale pin may be provided on the piston, extending through the cap, to provide an indication of the position of the valve member.

An elbow or tee pipe member is preferrably provided at the outlet of the control apparatus to prevent erosion of rubber hosing connected between the control apparatus and its respective gun.

In the drawings, wherein a preferred embodiment-of this invention is illustrated, and like numerals are used throughout to designate like parts;

FIG. 1 is a view in elevation of the fluid delivering system of this invention;

FIG. 2 is a cross-sectional view with certain parts in elevation, taken at 22 in FIG. 1, and showing the fluid pressure control apparatus of this invention.

FIG. 2A is an exploded view taken at 2A in FIG. 2.

FIG. 3 is a cross-sectional view taken at 33 in FIG. FIG. 4 is a cross-sectional view taken at 44 in FIG. FIG. 5 is a cross-sectional view taken at 5-5 in FIG. FIG. 6 is a cross-sectional view taken at 66 in FIG. FIG. 7 is a cross-sectional view taken at 77 in FIG. FIG. 8 is a partial view identical to FIG. 2, but with the valve member shown unseated; and

FIG. 9 is a view in elevation of the apparatus of FIG. 2 with a modified outlet connection.

Referring now to the drawings, in FIG. 1 the fluid delivery system of this invention is illustrated as including a pump P of conventional design having a plunger assembly M driven by a prime mover (not shown) and a high pressure fluid end F. Fluid end F has an inlet 10 connected to a source of fluid (not shown) and an outlet 11. A plurality of nozzle or dump" guns, such as two guns G, and G illustrated, are generally connected through a common manifold to outlet 11, however, according to the present invention a unitary control as sembly 12 including two fluid pressure control apparatus 12A and 128 for maintaining a substantially constant load on pump P is connected at an inlet to out let 11, and guns G, and G are each connected to the outlets of assembly 12 by hoses l3 and 14 respectively. Guns G, and G may be any of many designs of dump guns, however, for illustrative purposes they are shown as similar to the gun disclosed in US. Pat. application of Amos Pacht, Ser. No. 278,113, filed Aug. 4, 1972, now US. Pat. No. 3,765,607, entitled High Pressure Fluid System and Nozzle and Valve Assembly Therefor, and assigned to the assignee of the present application. Guns G, and G each include a valve housing 15 having a valve threin, high pressure nozzle outlet 16, a low pressure dump outlet 17, and a handle and trigger mechanism 18 for actuating the valve and directing fluid between either nozzle 16 or dump outlet 17. Guns G, and G typically may be used in high pressure water blasting for cleaning applications, in which case the water pressure at the guns may reach 10,000 psi and over when flow is through nozzle 16, and only several hundred pounds or less when water is dumped. The water pressures at guns G, and G are determined by the size of the orifices in nozzles 16, and the flow rate of pump P.

The details of a preferred form of control assembly 12 are shown in FIGS. 2-8, wherein for purposes of this description only reference will be made to the parts as being up or down (or lower or upper) because of the orientation of FIG. 2. Since apparatus 12A and 12B of assembly 12 are identical (except as herein noted),

only apparatus 12A is shown in FIGS. 2 and 4-8. As illustrated in FIG. 1, control assembly 12 includes five smaller blocks or sub-housings 19, 20, 20', 21, and 21, suitably bored, bolted together to form unitary control assembly 12 including the control apparatus 12A and 123 for both guns G, and G If desired, control apparatus 12A and 128 can be provided as separate units each connected between one of the guns of the fluid discharge systems and the outlet of pump P, however, with the arrangement illustrated, assembly 12 also serves as a manifold for delivering water from pump P to a plurality of guns.

For this purpose, block 19 includes a cylindrical bore 22 traversing it which functions as a water inlet and is connected by a suitable coupling 23 and piping to out let 11 of pump P. The other end of bore 22 may be closed by a plug 23a. Block 19 is divided into two identical side-by-side sections 19A and 1913 as shown in either side of an imaginary line 19C through FIG. 3, section 19A being shown in cross-section in FIG. 2, and sections 19A and 19B providing part of control apparatus 12A and 128 respectively. Each such chamber 25 connected to inlet 22 by passageway 24, and a central cylindrical valve actuator chamber 26 spaced from chamber 25 and connected therewith by a center bore 27. Block 19 also is bored to include a part of a by-pass fluid passageway 28 connected to inlet passageway 24 and a part of a fluid pressure sensing passageway 29 connected to chamber 26. Block 20 (one identical such block being provided for each of apparatus 12A and 12B) is bored to include a fluid outlet passageway 30 communicating between the bottom of chamber 25 and an outlet port 30A for sections 19A of apparatus 12A, and continuations of each of passageways 28 and 29 connecting these passageways into outlet passageway 30. Outlet port 30A may be connected to an elbow 13A to which hose 13 connected to gun G, is connected. A valve seat 31 having a central bore 32 in line with outlet passageway 30 is mounted in chamber 25 and extends between blocks 19 and 20. When block 20 is mounted on block 19, such as by bolts 33, valve seat 31 and a pin 34 may serve as dowels for aligning the various flow passageways described. Chamber 25 in both block 19 and 20 is sealed about the periphery of valve seat 31 by O-ring seals as shown in FIG. 2.

Valve chamber 25, formed when blocks 19 and 20 are bolted together, includes lower portion 25A in which valve seat member 31 is mounted, and a slightly smaller diameter upper portion 258 into which a movable valve member 35 extends for seating and sealing engagement with valve seat member 31, and into which inlet passageway 24 connects. Valve member 35 and valve seat 31 form a valve for permitting and interrupting flow of fluid through chamber 25 from inlet 22 to outlet 30A. Flow passageways 24 and 30 and valve chamber 25 thus form a main flow passageway through which water may flow from inlet 22 to outlet 30A except when valve member 35 is seated on valve seat member 31. When this occurs, flow from inlet 22 to outlet 30A may be through by-pass passageway 28.

As shown in FIGS. 2 and 6, block 20 includes a partially threaded bore 36 extending from the exterior of block 20 to connect with by-pass passageway 24, and a removable orifice means 37 is inserted into bore 36 and extends therefrom into by-pass passageway 24 for simulating the nozzle on gun G Orifice means 37 is preferrably a threaded insert member which may be readily removed and replaced by another such means having a different size orifice when the nozzle of the gun is changed, and includes a threaded head portion 37A, and an elongated orifice insert 37b having a plurality of inlet ports 37c and an outlet orifice 37d for discharging water into passageway 30. O-ring seals are provided as shown to seal passageway 24 and bore 36 around the periphery of insert member 37.

Movable valve member 35 includes a flat seating disk 35a on its lower end in chamber 25 for seating on valve seat member 31, and an elongated stem portion 35b extending up through bore 27 with a close sliding fit and into chamber 26. his preferred that disk 35a of valve member 35 be flat to permit seating without misalignment or problems of concentricity that may occur with a tapered valve member and seat, and that disk 35a ex tend about the periphery of the stern of member 35 in a manner to permit fluid pressure to act on the top surface of the disk during seating. Bore 27 is sealed against flow of fluid from both chambers 25 and 26 along the periphery of stem 35b by the seal 38 shown in FIG. 2A, which includes an O-ring with a backup ring on either side of it. The upper end of stem 35b is threaded and includes a small pin 39 extending upwardly from it. A cylindrical, movable piston 40 having a threaded bore 41 is provided in chamber 26 with a close sliding fit and the upper end of stem 35b is threaded into bore 41 until pin 39, which serves as a stop, abuts the upper end of bore 41. The diameter of the lower end of piston 40 is larger than the diameter of seat 35a so that the surface area of the lower end of piston 40 extending about stem 35!; is greater than the surface area of the top of disk 35 a extending about stem 35b.

The upper end of piston 40 is of smaller diameter than the lower part thereof so that an annular shoulder 42 is formed on which a coil spring 43 may be mounted. The upper end of chamber 26 is closed by member 21 mounted on block 19 by bolts, and member 21 includes a cylindrical bore 44 which functions as an extension of chamber 26. Member 21 thus serves as a cap, as an abutment for compressing spring 43 and a stop for the upward movement of piston 40, so that disk 35a need not be used as a stop. Piston 40 may include a tell-tale pin 45 extending from its upper end through block 21 to give an indication of the position of piston 40, and thus valve member 35, which moves with piston 40, in apparatus 12A.

Spring 43 must be large enough to force piston 40 down and thus seat disk 350 on valve seat member 31 when the water pressure in outlet 30A is low, i.e., when gun G, is dumping, but not so large that the spring cannot be overcome when the pressure in outlet 30 rises in response to actuation of gun 6,. Also, since block 21 is movable, the size of spring 43 can be changed to compensate for pumps of different flow rates and, if needed, a larger block 21 can be used to accommodate a larger spring. By way of example, if the pressure at outlet 30A is 100 pounds when gun G, is dumping, and 5,000 psi or high when discharge is through its nozzle, spring 43 can be such that pressures of 1,000 pounds or greater at outlet 30A will overcome it.

In operation, when gun G, is dumping (this description of operation also being applicable to apparatus 128 and gun G so that the pressure at outlet 30A is low, then the valve in chamber 25 is closed and flow from inlet 22 to outlet 30A is through by-pass passageway 24 and orifice 37d, which as previously noted, is

the same size as the orifice in nozzle 16 of gun G,. Thus, the pressure on the inlet side of passageway 24 rises to substantially the same pressure it would be if flow were through nozzle 16, and pump P has substantially the same load. The higher pressure in inlet 24 is also communicated to the top of chamber 25 and acts on the top side of disk 35a to further aid in keeping the valve in chamber 25 closed. However, when trigger 18 in gun G, is activated, to direct water through nozzle 16, the water pressure on the outlet side of orifice 37d also rises to a higher value and water at this higher pressure passes through passageway 29 to the lower end of chamber 26 where it acts on the lower end of piston 40, and it also passes up passageway 30 and bore 32 in valve seat 25 to act on the lower end of valve disk 35a. The pressures on either side of valve disk 35a are offset against each other and the pressure acting on piston 40 overcomes the force of spring 43 and moves piston 40 up against block 21 as shown in FIG. 8, moving disk 35a off of and out of sealing engagement with valve seat 31. As shown in FIG. 8 stern 35b stops in bore 41 of piston 40, and piston 40 stops against block 21 so that a clearance is provided between the upper side of disk 35a and the upper wall of chamber 25. This clearance helps to balance the pressure on either side of disk 35a in chamber 25 so that the size of spring 43 can be smaller. Thus, when trigger mechanism 18 is released and the pressure in outlet 30a is reduced to substantially the dumping pressure of gun G,, spring 43 will again force valve member 35 to close on seat 31.

When water is being discharged through orifice 37d a blast of water will be present at outlet 30a and will possibly damage a rubber hose connected to the outlet, such as hose 13. It is thus preferred that some sort of means be connected to outlet to break up this blast of water before it can damage the connecting hose. One such means is the pipe elbow connection 13A shown in FIG. 2. FIG. 9 illustrates another such means which may be a standard tee joint of pipe 46 connected to outlet 30a.

Thus, as can be seen from the above description, control apparatus 12 provides a substantially constant load to pump P and substantially constant inlet pressures for guns G, and G despite the large pressure changes occuring at the guns, which may occur in any sequence during actual use of the guns. This is true whether both guns are dumping, providing a high pressure blast of water, or one is dumping and the other blasting. Also, different size nozzle openings in guns G, and G can be simulated by inserting different size orifices 37d in the respective apparatus 12A and 128, as required. Thus, if nozzles 16 are of different size, then inserts 37 of different size can be provided in apparatus 12A and 1213. Of course, only two guns with two control apparatus are shown, but more than two guns and their respective control apparatus can be provided.

From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with otheradvantages which are obvious and which are inherent to the appa-- ratus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. In a fluid system for supplying a high pressure stream of fluid, including a pump having a low pressure inlet adapted to be connected to a source of fluid and a high pressure outlet, and at least one nozzle gun having an inlet, a high pressure discharge nozzle, a relatively low pressure dump outlet, and actuating means for diverting flow between said nozzle and said dump outlet, the improvement in said system comprising at least one fluid pressure control apparatus having an inlet adapted to be connected to the outlet of said pump, an outlet adapted to be connected to the inlet of one of said guns, a first flow passageway connected between its inlet and outlet, a second flow passageway connected between its inlet and outlet for bypassing said first passageway, valve means in said first passageway responsive to the fluid pressure at its outlet to move between a first position permitting flow through said first passageway when the gun connected thereto is actuated to discharge fluid through its nozzle, and to a second position wherein flow through said first passageway is interrupted and diverted through said second passageway when said gun is dumping, and orifice means mounted in said second passageway and having an opening therethrough that is substantially the size of the nozzle opening of the gun connected to the outlet of said control means.

2. The system of claim 1 wherein each of said control apparatus includes pressure responsive means for moving said valve means between said first and second positions, and a third flow passageway connected to the outlet of said control means and conducting fluid from said outlet to said pressure responsive means.

3. The system of claim 2 wherein said first passageway includes a valve chamber therein and said apparatus includes a piston chamber to which said third flow passageway is connected, and wherein said valve means includes a valve seat in said valve chamber and a valve member having a disk member in said chamber and a stem portion extending from said valve chamber into said piston chamber, and further including a movable piston in said piston chamber connected to said stem portion and responsive to fluid pressure in said third passageway to move said valve member out of sealing engagement with said valve seat, and means for urging said piston against such fluid pressure to cause said valve member to be seated on said valve seat.

4. The system of claim 3 wherein said last mentioned means is a spring and said apparatus includes a removable cap for compressing said spring and urging it against said piston, said cap also serving as a stop for the movement of said piston against the force of said 8 spring.

5. The system of claim 1 wherein said orifice means is provided by a removable insert in said second passageway.

6. The system of claim 1 wherein at least two such pressure control apparatus are provided in a unitary assembly having a common fluid inlet.

7. Pressure control apparatus for connection in a high pressure fluid delivery system between a pump and a gun assembly having a high pressure nozzle outlet and a dump outlet, for maintaining a substantially constant load on the pump, said apparatus comprising, in combination: an inlet adapted to be connected to the outlet of such a pump, an outlet adapted to be connected to such a gun, a main passageway connected between said inlet and said outlet; valve means in said passageway for permitting or interrupting flow of fluid from said inlet through said main passageway to said outlet, a by-pass passageway connected between said inlet and said outlet for permitting flow of fluid from said inlet to outlet to by-pass said main passageway, orifice means in said by-pass passageway for providing a restriction to fluid flow substantially the same size as the nozzle on said gun, and means responsive to fluid pressure at the outlet of said apparatus for causing said valve means to interrupt flow through said main passageway when the fluid pressure at said output is relatively low, whereby such flow is through said by-pass passageway, and for causing said valve means to permit flow through said main passageway when the pressure at said outlet is relatively high.

8. The apparatus of claim 7 wherein said valve means includes a valve member having a flat seating disk and a valve seat having a flat seating surface.

.9. The apparatus of claim 8 wherein said valve seat is a removable member.

10. The apparatus of claim 7 wherein said main passageway includes a valve chamber therein'and further including a piston chamber and a third flow passageway connected between said piston chamber and said outlet, and wherein said valve means includes a valve seat in said valve chamber and a valve member having a disk member in said chamber and a stem portion extending from said valve chamber into said piston chamber, and further including a movable piston in said piston chamber connected to said stem portion and responsive to fluid pressure in said third passageway to move said valve member out of sealing engagement with said valve seat, and means for urging said piston against such fluid pressure to cause said valve member to be seated on said valve seat.

11. The system of claim 10 wherein said last mentioned means is a spring and said apparatus includes a removable cap for compressing said spring and urging it against said piston, said cap also serving as a stop for the movement of said piston against the force of said spring. 

1. In a fluid system for supplying a high pressure stream of fluid, including a pump having a low pressure inlet adapted to be connected to a source of fluid and a high pressure outlet, and at least one nozzle gun having an inlet, a high pressure discharge nozzle, a relatively low pressure dump outlet, and actuating means for diverting flow between said nozzle and said dump outlet, the improvement in said system comprising at least one fluid pressure control apparatus having an inlet adapted to be connected to the outlet of said pump, an outlet adapted to be connected to the inlet of one of said guns, a first flow passageway connected between its inlet and outlet, a second flow passageway connected between its inlet and outlet for bypassing said first passageway, valve means in said first passageway responsive to the fluid pressure at its outlet to move between a first position permitting flow through said first passageway when the gun connected thereto is actuated to discharge fluid through its nozzle, and to a second position wherein flow through said first passageway is interrupted and diverted through said second passageway when said gun is dumping, and orifice means mounted in said second passageway and having an opening therethrough that is substantially the size of the nozzle opening Of the gun connected to the outlet of said control means.
 2. The system of claim 1 wherein each of said control apparatus includes pressure responsive means for moving said valve means between said first and second positions, and a third flow passageway connected to the outlet of said control means and conducting fluid from said outlet to said pressure responsive means.
 3. The system of claim 2 wherein said first passageway includes a valve chamber therein and said apparatus includes a piston chamber to which said third flow passageway is connected, and wherein said valve means includes a valve seat in said valve chamber and a valve member having a disk member in said chamber and a stem portion extending from said valve chamber into said piston chamber, and further including a movable piston in said piston chamber connected to said stem portion and responsive to fluid pressure in said third passageway to move said valve member out of sealing engagement with said valve seat, and means for urging said piston against such fluid pressure to cause said valve member to be seated on said valve seat.
 4. The system of claim 3 wherein said last mentioned means is a spring and said apparatus includes a removable cap for compressing said spring and urging it against said piston, said cap also serving as a stop for the movement of said piston against the force of said spring.
 5. The system of claim 1 wherein said orifice means is provided by a removable insert in said second passageway.
 6. The system of claim 1 wherein at least two such pressure control apparatus are provided in a unitary assembly having a common fluid inlet.
 7. Pressure control apparatus for connection in a high pressure fluid delivery system between a pump and a gun assembly having a high pressure nozzle outlet and a dump outlet, for maintaining a substantially constant load on the pump, said apparatus comprising, in combination: an inlet adapted to be connected to the outlet of such a pump, an outlet adapted to be connected to such a gun, a main passageway connected between said inlet and said outlet; valve means in said passageway for permitting or interrupting flow of fluid from said inlet through said main passageway to said outlet, a by-pass passageway connected between said inlet and said outlet for permitting flow of fluid from said inlet to outlet to by-pass said main passageway, orifice means in said by-pass passageway for providing a restriction to fluid flow substantially the same size as the nozzle on said gun, and means responsive to fluid pressure at the outlet of said apparatus for causing said valve means to interrupt flow through said main passageway when the fluid pressure at said output is relatively low, whereby such flow is through said by-pass passageway, and for causing said valve means to permit flow through said main passageway when the pressure at said outlet is relatively high.
 8. The apparatus of claim 7 wherein said valve means includes a valve member having a flat seating disk and a valve seat having a flat seating surface.
 9. The apparatus of claim 8 wherein said valve seat is a removable member.
 10. The apparatus of claim 7 wherein said main passageway includes a valve chamber therein and further including a piston chamber and a third flow passageway connected between said piston chamber and said outlet, and wherein said valve means includes a valve seat in said valve chamber and a valve member having a disk member in said chamber and a stem portion extending from said valve chamber into said piston chamber, and further including a movable piston in said piston chamber connected to said stem portion and responsive to fluid pressure in said third passageway to move said valve member out of sealing engagement with said valve seat, and means for urging said piston against such fluid pressure to cause said valve member to be seated on said valve seat.
 11. The system of claim 10 wherein said last mentioned means is a spring and said apparatus includes a removable cap for compressing said spring and urging it against said piston, said cap also serving as a stop for the movement of said piston against the force of said spring. 